Puttabasavaiah, Suneetha

2596 Background: Docetaxel (D) is an anti-mitotic drug metabolized by the cytochrome P450 (CYP) 3A4 enzyme. While case reports have demonstrated a potential association of CYP3A inhibitor use with severe toxicity in D treated patients (pts), there are no data whether co-administration of CYP3A inhibitors with D increases the rate of hospitalization and/or death. Methods: A retrospective cohort of pts treated with D at the Mayo Clinic Rochester from 1/1/09-10/1/11 was identified. Information regarding D and concomitant chemotherapy (starting dose and dose reductions), type of CYP3A inhibitor, growth factor use, hospitalizations and deaths was abstracted. Time to event analyses (either hospitalization or death) were conducted using Kaplan-Meier estimates and proportional hazards modeling. Results: 384 pts (median age 63, range 20-93) received D as monotherapy (48%) or as multi-agent chemotherapy (52%) for a median of 4 cycles. 56 pts were co-administered CYP3A inhibitors (45 moderate, 11 strong). 90 pts were hospitalized during D chemotherapy and 15 died. The mean time to hospitalization was significantly shorter in pts treated with a mod/strong CYP3A inhibitor (186 days) vs not treated (408 days) (p=0.02) . While time to death was not significantly different based on inhibitor use (111 vs. 177 days, p=0.49), time to first event (hospitalization or death) varied significantly according to those on inhibitors (187 days) versus not (397 days) (HR: 1.78, p=0.02). Time dependent analyses indicated that use of multiage chemotherapy (combination vs D monotherapy; HR 1.96, p= 0.002) and chemotherapy dose reduction of either D (HR 0.54, p<0.01) or other chemotherapy (HR 0.61, p=0.02) were significantly associated with the risk of an event. In a multivariate analysis, moderate/strong CYP3A inhibitor use was associated with a higher risk of any event (HR 1.79, p<0.02), independent of the use or dose of either multi-agent chemotherapy or D dose. Conclusions: These are the first data to demonstrate that co-administration of CYP3A inhibitors with D increases the risk of hospitalization and/or death. Oncologists should reconcile medications prior to D administration and mod/strong CYP3A inhibitors should be avoided or used with caution.

1557 Background: Peripheral neuropathy (PN), a common and intrusive side effect of chemotherapy in clinical trials, has been assessed via the clinician-rated common terminology criteria for adverse events (CTCAE) and/or patient-reported outcome (PRO) measures (Morton, ASCO, 2005). We assessed the relative sensitivity of CTCAE and PRO measures for evaluating interventions for preventing and ameliorating CIPN. Methods: Data from285 patients in two prevention trials (N05C3, N04C7) and 432 patients from three intervention trials (N00C3, N01C3, N06CA) were analyzed separately. CTCAE version 3.0 item for neuropathy was compared to 2 NCCTG numerical analogue CIPN items, 6 EORTC CIPN20 individual items, 2 McGill Pain Questionnaire items, and one Brief Pain Inventory item. The sample size provided over 80% power to detect a true Spearman rank correlation of 0.15 assessed the relationship between CTCAE and PRO measures. Results: Results from both the prevention and treatment trials were similar in terms of the relationship between the CTCAE and PRO measures. No correlation coefficients between the CTCAE and any of the PRO items at baseline were above 0.35, with the majority around 0.2. Higher scores for the numbness items were observed than for the CTCAE in 47% of the patients at baseline and 39% during treatment in the treatment trials. Many patients had severe numbness PRO scores but mild CTCAE scores (12%) at baseline and (8%) during treatment in the treatment trials. Results for the numbness and tingling PRO measures were redundant. The correlations of the CTCAE with pain were weak, all below 0.35 at baseline with differences as much as 29 points on average on a 0-100 transformed scale. Conclusions: The CTCAE and PRO measures of PN measure different constructs. The CTCAE includes both functional and ADL/motor aspects which may or may not be related to the singular constructs of pain, numbness, tingling, or adjectival characteristics of pain assessed by the PRO measures. The two measures cannot be used in place of each other.

BACKGROUNDPostmenopausal women with breast cancer receiving aromatase inhibitors are at an increased risk of bone loss. The current study was undertaken to determine whether upfront versus delayed treatment with zoledronic acid (ZA) impacted bone loss. This report described the 5‐year follow‐up results.METHODSA total of 551 postmenopausal women with breast cancer who completed tamoxifen treatment and were undergoing daily letrozole treatment were randomized to either upfront (274 patients) or delayed (277 patients) ZA at a dose of 4 mg intravenously every 6 months. In the patients on the delayed treatment arm, ZA was initiated for a postbaseline bone mineral density T‐score of <‐2.0 or fracture.RESULTSThe incidence of a 5% decrease in the total lumbar spine bone mineral density at 5 years was 10.2% in the upfront treatment arm versus 41.2% in the delayed treatment arm (P<.0001). A total of 41 patients in the delayed treatment arm were eventually started on ZA. With the exception of increased NCI Common Toxicity Criteria (CTC) grade 1/2 elevated creatinine and fever in the patients treated on the upfront arm and cerebrovascular ischemia among those in the delayed treatment arm, there were no significant differences observed between arms with respect to the most common adverse events of arthralgia and back pain. Osteoporosis occurred less frequently in the upfront treatment arm (2 vs 8 cumulative cases), although this difference was not found to be statistically significant. Bone fractures occurred in 24 patients in the upfront treatment arm versus 25 patients in the delayed treatment arm.CONCLUSIONSImmediate treatment with ZA prevented bone loss compared with delayed treatment in postmenopausal women receiving letrozole and these differences were maintained at 5 years. The incidence of osteoporosis or fractures was not found to be significantly different between treatment arms. Cancer 2015;121:2537–2543. © 2015 American Cancer Society.